Keyboard Feedback Problems

  • Thread starter Thread starter Carrotstherabbi
  • Start date Start date
Steenamaroo said:
It could simply be that it's unbalanced audio and your cables are near other cables and gear,
but it's still odd that it's a new problem.

The best bet is probably to use the balanced L+R outputs on the rear, straight into the audio box.
TRS cables at both ends.

Do you have any to try?
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I'm sorry, I'll continue this tomorrow. I greatly appreciate the time you spent.
 
Steenamaroo said:
;)

Going into XLR isn't a good idea.
If you put phantom power on by mistake you could seriously damage your keyboard and/or interface.
On top of that, the XLR input expects a very low level of signal, so a line level going in isn't a good match.

TRS to TRS is perfect. Both line level, balanced, made for eachother.
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Ill have to purchase some then. I guess I'll be back...
 
The trouble with all these things can often annoyingly be just down to pieces of kit that don't like each other. I collaborate on some music projects with a colleague and we have virtually identical equipment in terms of the crucial bits of hardware and software - but - we have different interfaces. Mine is multi channel, he had a Lexicon. Fine. The same keyboard as I have plugged into it. Then he upgraded to windows 10 and discovered Lexicon dumped their customers and are not supporting the interface on windows 10. He bought a Focusrite. Instantly he had all the problems described here. Weird bus noise - with the mouse zipping noises, a persistent low level hum and a real mess. Turned out the focusrite was drawing more current than the USB port was happy providing. He bought a different brand and returned the focusrite - A Roland. Normal service restored. However I borrowed the same unit from another friend, which produced the same effect - but cured totally when connected via a powered hub that could supply the right current. If you can borrow one - I'd encourage you to try this, weird though it sounds as your problem is so similar to his.

You also mentioned that the keyboard audio was quiet and thin, lacking bass. This often happens with connections to the stereo output from headphones when the cable connection ends up using the keyboard left for one connection and keyboard right for the return - you accidentally are only hearing the difference between the left and right. This can happen too using the keyboard left and right jacks if you try to combine them in an adaptor to go into a single jack input.
 
I have discovered that the Fantom 8 is, unusually for a synth, powered from an IEC 3core lead.

Pretty sure therefore that OPs' woes are due to an earth (aka ground, aka hum) loop. For sure also, headphone jacks output L&R and this needs splitting or resistively combing to MONO to avoid weird cancellation effects. The L and R line outs SHOULD work but even there a transformer isolator would be a good buy ASAP.

Just to quash an oft repeated myth? Headphone outputs are NOT super hot! Often just line level through a buffer amp to deliver more CURRENT not voltage. Considering most cans produce about 100dB SPL for around 1 volt there is no need for higher drive voltages. One V is of course around +4dBu.

Dave.
 
ecc83 said:
Just to quash an oft repeated myth? Headphone outputs are NOT super hot! Often just line level through a buffer amp to deliver more CURRENT not voltage. Considering most cans produce about 100dB SPL for around 1 volt there is no need for higher drive voltages. One V is of course around +4dBu.

Dave.
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Million reasons not to use a headphone output and I pick the wrong one.
Thanks Dave.
 
Well, turned right up they CAN be super hot--just as plugging a set of headphones into a line level output can result in a faint whisper of sound.

However, as has been said, the simple expedient of turning down the headphones can put things at a usable level.

Just as an example, I'm currently involved in a theatre show. I do all my music and effects playback from a laptop computer which runs via a USB interface (with balanced outs) into the theatre mixer. However, I'm paranoid enough that I have a back up system (this show has an almost continuous soundscape) which is a small netbook loaded up with the playback software and all the sounds. For this one, I just take the headphone out via an adaptor cable into two line level inputs on the mixer. In order to get the levels from the netbook roughly the same as the "good" interface (i.e. input gains and faders set to the same levels) I have to run the netbook software level control down at approximately 1/4 the maximum (and max is the default).

So, as has been said, headphones out don't HAVE to be super hot--but it usually takes some fiddling with gain controls to turn them down to a suitable level.
 
Bobbsy said:
Well, turned right up they CAN be super hot--just as plugging a set of headphones into a line level output can result in a faint whisper of sound.

However, as has been said, the simple expedient of turning down the headphones can put things at a usable level.

Just as an example, I'm currently involved in a theatre show. I do all my music and effects playback from a laptop computer which runs via a USB interface (with balanced outs) into the theatre mixer. However, I'm paranoid enough that I have a back up system (this show has an almost continuous soundscape) which is a small netbook loaded up with the playback software and all the sounds. For this one, I just take the headphone out via an adaptor cable into two line level inputs on the mixer. In order to get the levels from the netbook roughly the same as the "good" interface (i.e. input gains and faders set to the same levels) I have to run the netbook software level control down at approximately 1/4 the maximum (and max is the default).

So, as has been said, headphones out don't HAVE to be super hot--but it usually takes some fiddling with gain controls to turn them down to a suitable level.
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Now come along Robert! You should know by now that I am a pedantic old bugger! WTF does "1/4 way down" mean? What line levels are you feeding the mixer?

I agree a domestic neg 10 setup will find headphone outs a bit hotter (at around -6dBV?) but not, I would aver if you are working at +4dBu? 'S'all relative.

In any case the vast majority of headphone amplifiers run from the same supply rails as the rest of the mixer etc, + and - 12 to 18 volts so their maximum op voltage is going to be about the same as the line outs (or, if the line outs are electronically balanced, i.e. two amps, 6dB lower!) No idea how the cans amps are powered in the laptop, 12V single rail?

Of course, headphone outputs are usually at low source impedance. 100 Ohms or less and, unlike a LINE output have a much greater current capability, this is why cans on a line OP are so weak, the OP chip is current limiting. If you can find some, 600 Ohm headphones can be driven quite loudly from a proper "pro" line source which should have an OPZ of 100 Ohms or lower.

Dave.
 
Ah c'mon Dave. I'm in a theatre with an impatient director and cast--I don't have time to get out my multimeter and do "real" measurements.

All I can say is that, in a theatre with a pro mixer working at +4dBu, if I set the channel gains the same as for a "real" line level input and the channel faders at zero, I have to click that little loudspeaker icon in the bottom right of my screen and turn the slider down to only about a quarter of the way up from the bottom. What I DO have to confirm that these settings give the proper levels is an RTA that lets me accurately measure the level in the auditorium from a fixed spot.

I assume it would have to be turned down even more with a domestic -10dBV set up.

The other thing with headphone outs is that there's no specific standard--some are louder and some are quieter. This doesn't mean that you can't usually find a happy level--it just means that my "quarter of the way up on the slider" doesn't necessarily give the correct levels on somebody else's gear.
 
Bobbsy said:
Ah c'mon Dave. I'm in a theatre with an impatient director and cast--I don't have time to get out my multimeter and do "real" measurements.

All I can say is that, in a theatre with a pro mixer working at +4dBu, if I set the channel gains the same as for a "real" line level input and the channel faders at zero, I have to click that little loudspeaker icon in the bottom right of my screen and turn the slider down to only about a quarter of the way up from the bottom. What I DO have to confirm that these settings give the proper levels is an RTA that lets me accurately measure the level in the auditorium from a fixed spot.

I assume it would have to be turned down even more with a domestic -10dBV set up.

The other thing with headphone outs is that there's no specific standard--some are louder and some are quieter. This doesn't mean that you can't usually find a happy level--it just means that my "quarter of the way up on the slider" doesn't necessarily give the correct levels on somebody else's gear.
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Fairy nuff Bobbs! Just want to clear up the fact that headphone jack do not, as general rule, deliver more VOLTAGE drive than a decent line output.
Headphone levels variable? Agreed and so are line outs on AIs! Oh! for a bit of standardization.

If noobs are looking in and find this discussion esoteric and mind boggling I can assure you that getting to grips with audio levels is not that hard and the effects of "loading" can be understood fairly easily with a bit of study of Ohms Law and thinking about devices as "black boxes".

Dave.
 
The TRS did the trick. I only had TR cables and now the sound is just about gone. Thank you for the suggestion!
 
The problem I was having seemed to mostly fix when I switched from TS to TRS cables. There is still some static due to my computer but I'll figure that out, along with my L and R outputs. But thank you everyone for the help and may this thread help others!
 
Good deal. Glad to hear it is working for you now. The mouse/usb noise could be poor grounding in the computer. Not much you can do about that. Try a different USB port. If you have a regular computer, you might try buying a USB card to see if that helps. If you have a laptop, unplug it from the wall and check for noise. Some laptops have poor power supplies.
 
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